10 Most Common PV System Anomalies Detected by Drones (Part A)

Solar companies involved in the design, build, management, and/or maintenance of PV systems are increasingly adopting UAS (drones) to replace field work that takes large amounts of time and money. Field walks, IV curve tests, voltage checks, and handheld thermal scans of modules are just a few examples of tasks being replaced with drones by Asset Management and O&M teams around the world. Drones set up with both thermal (IR) and high-resolution (RGB) imaging cameras allow for commonly mislabeled anomalies, ie. soiling, to be properly identified and not mistaken for module hot spots.

In this post, we are going to cover the range of PV system anomalies that can be identified during an aerial solar farm inspection performed by a drone. Before we get started, it’s important to make sure you’re familiar with the general workings of PV systems and how they operate. This is a must when it comes to inspecting solar farms effectively with a drone. Here’s a quick breakdown:

Solar farm → A solar farm can have hundreds of rows→ Single or multiple strings are within a row→ Strings are made up of modules→ Modules are made up of several photovoltaic cells (Polycrystalline, amorphous, TPV, multi-junction)

1. Module Level Issues

Possibly the most common anomaly discovered during aerial drone inspections are module level anomalies. Several types of anomalies can appear within the frame of a PV module, including cell hot spots, multi-cell hot spots, and activated bypass diodes. Although not as severe as string issues, module anomalies, especially when in abundance can drastically reduce the efficiency of a PV system, and when left unattended over long periods of time, might develop into a more serious issue.

2. Shadowing

Shadowing of PV modules, strings, and rows is a commonly identified anomaly from a drone inspection. Shadowing can be caused by vegetation, surrounding structures, and even adjacent solar rows. Although most occurrences of shadowing do not require PV technician attention, shadowing due to vegetation can lead to larger problems if not addressed earlier.

Identifying shadowing in both the IR (thermal) and high-resolution drone inspection imagery can help Asset Management and O&M teams more effectively spend budgeted maintenance costs on vegetation management. We recently helped a solar plant manager in south-central Asia use his internal drone program and regular drone inspections to make more informed decisions on when to dispatch his vegetation management contractor.

3. Shattering & Soiling

Some issues are detectable through the RGB imagery taken during data collection. These anomalies are mostly associated with the physical attributes of the farm. Shattering (cracked glass) of panels due to module installation, maintenance, racking shifts, or severe weather is an anomaly that can be easily detected with RGB imagery.

Soiling from dust, bird droppings, and other debris can also heavily affect the efficiency of PV modules.

4. String Level Issues

String issues are the most severe (and easily detectable) anomalies when flying and analyzing your inspection data. Strings (composed of modules) can be warm, offline, have reversed polarity, or completely fail which causes large energy losses within the PV system.

5. Tilt Tracker Alignment and Racking Issues

If the solar farm is built on tilt trackers rows and panels can get stuck in a certain orientation reducing their efficiency. Not all solar sites are built on tilt trackers but, those that need to be thoroughly assessed for angle discrepancies caused by installation, or maintenance errors.

Are you interested in learning more about UAS, drone inspections of solar assets, and having your data converted PV analytics and system reports? If so, please contact us here and our team will be in touch.